The present invention relates to power tools and, more particularly, to motors for power tools.
All electric power tools, whether AC or DC powered, utilize motors to drive the outputs of the tools. Motors are a critical part of the power tool. Designers strive to improve various aspects of the motors in power tools. Specifically, designers strive to reduce motor size while increasing motor output. Designers try to reduce heat created by the motor. Designers strive to reduce the number of parts associated with the motor. Also, designers strive to reduce the possibility of demagnetization of the motor during operation. In short, motor improvement improves the overall performance of the power tool.
The present invention provides the art with an improved motor assembly. The motor includes various features which reduce the total number of parts in the motor, improve assembly, enable simpler manufacturing techniques, as well as increase the resistance of the motor to demagnetization.
In accordance with a first aspect of the invention, a power tool includes a motor comprising an end cap. The end cap has a base with a mechanism on the base to secure the base with the motor can. A recess is in the base to receive a bearing. The recess also includes an aperture to receive an armature shaft. A bearing is positioned within the recess. A portion of the base is disformed adjacent to the recess to retain the bearing in the recess. The deformation may be an annular shoulder around the entire bearing or it may be segmented with a number of segments deformed in a circular pattern around the bearing. Also, a method of retaining a bearing in the motor end cap includes positioning the bearing into the recess, deforming the motor end cap adjacent the recess, and fixing the bearing in the recess.
In accordance with a second aspect of the invention, the power tool includes a motor comprising an armature shaft assembly. The armature shaft assembly includes a shaft which includes a plurality of stakes in its outer peripheral surface. The stakes extend a desired length along the longitudinal axis of the shaft. A plurality of laminates are positioned on the shaft. The plurality of laminates have an aperture which slips onto the shaft and is then pressed on and retained by the plurality of stakes on the shaft. A retaining member which includes a bore is also slipped onto the shaft. The retainer is pressed onto the plurality of stakes to maintain position of the retainer on the shaft. The retainer is a metal part. The retainer, along with the laminates, are coated to provide additional resistance against movement with respect to the shaft.
According to a third aspect of the invention, a power tool includes a motor assembly comprising a motor can having two ends. Each end includes an end cap. An armature mechanism is rotatably positioned within the motor can. The armature mechanism includes a shaft with a portion of the shaft extending from one of the end caps to receive a pinion gear. A pinion gear is positioned on the shaft. The pinion gear includes a shoulder extending towards the end cap. The shoulder is adapted to limit movement of the armature mechanism in the motor can. The shoulder has a desired length to enable a clearance between a commutator and the other end cap in the event of movement of the armature mechanism.
According to a fourth aspect of the invention, a power tool includes a motor with a fan positioned on the armature. The armature is provided and the fan is coupled with the armature assembly. An adhesive is placed onto the fan to secure the fan to the armature assembly. The adhesive is a first color, generally bright yellow, when the adhesive is wet. The adhesive is enabled to cure to permanently fix the fan to the armature assembly. Upon curing, the adhesive changes color from a first color to a second color. Preferably, the second color is brown. This enables an assembly line worker to realize that the fan has either just been positioned onto the armature assembly, by viewing the bright yellow color, or that the fan adhesive is cured and the fan is fixed onto the armature assembly to enable further assembly of the motor.
In accordance with a fifth aspect of the invention, a power tool includes a motor which comprises an end cap secured with the motor can. The motor can includes a plurality of extending fingers. The end cap is provided with a plurality of recesses corresponding to the number of the plurality of fingers. The end cap is positioned with the motor cap such that the plurality of fingers mesh with the plurality of recesses. The extending fingers are cold worked to deform the fingers at the end cap. This deforming secures the end cap with the motor can via the plurality of deformed extending fingers. This method of attaching the end cap to the motor can also centers the end cap on the motor can.
In accordance with a sixth aspect of the invention, a power tool includes a motor which has an increased resistance to demagnetization. The motor comprises a motor can having two ends with end caps coupled with the ends of the motor can. An armature assembly is rotatably positioned within the motor can. A magnetic mechanism is positioned in the motor can. The magnetic mechanism includes a housing with at least one magnet secured to the housing. The housing includes at least one aperture with the at least one magnet including magnetic material which extends into the aperture filling the aperture with magnetic material. The increased magnetic material portion of the at least one magnet reduces the susceptibility to armature reaction demagnetization at that position. The housing may include a ring member which is positioned within the motor can. Also, when the ring member is used, the motor can may include at least one aperture aligned with the other aperture to receive additional magnetic material to increase the resistance to demagnetization. Also, the motor can itself may act as the housing and include the at least one aperture.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.